The invention is based on a diaphragm pressure regulator of the general type described by the preamble to the main claim. A diaphragm pressure regulator for regulating the fluid pressure in a system having fluid flowing through it is already known; this regulator has the disadvantage, however, that in its resting position it no longer seals effectively over the long term, so that fluid can leak out, and the system must first be refilled before operation can begin again, which may cause delays in response time or even functional interruptions.